9.6.3. Traffic Demand

Total traffic demand projected for the year 2050 for three of the long-range
scenarios is shown in Figure 9-26. The values shown
for the FESG model projection do not include military or general aviation traffic.
Military and general aviation fuel burned and emissions were estimated separately
for the year 2050; they were 3.1 and 1.8% of total fuel burned, respectively
(Fa1,2). The demand values shown for the EDF model include military as well
as freight demand, with projected billion tonne-km values converted to RPK.
The DTI model includes passenger, freight, and business jet traffic but excludes
military operations. The WWF model includes passenger and freight only, but
a demand value for 2041 was not published.

Although the FESG and EDF models use the same IS92 economic scenarios (IS92
population scenarios also are inputs to the EDF model), the traffic demand projections
for 2050 from the EDF model are higher than those of the FESG model by a factor
of 1.2 to almost 4, depending on the scenario. The DTI model, which does not
directly depend on the IS92 scenarios, projects a traffic demand about 80% that
of the FESG high case (Fe1,2). Clues to the reasons behind the large differences
in projected traffic demand between the FESG and EDF models can be found by
examining the details of the results of each model. The EDF model projects passenger
business and personal traffic in five world regions, plus military and freight
traffic. To make comparisons between the two models, the 45 traffic demand flows
(allocated from the global growth projection) in the FESG model were assigned
to the five regions used in the EDF model. Demand flows between two of the EDF-defined
regions were allocated by assigning 50% of the FESG traffic demand to each region.

On the previous page, Figure 9-27 shows a comparison
of traffic demand in 1990 and 2050 from the FESG and EDF models, with demand
sorted by region and/or type. The EDF base case demand (Eab) is compared with
the Fa1,2 demand scenario. Large differences in the distribution of demand between
the two models are apparent: The FESG model assigns the largest share of passenger
traffic in 2050 to the OECD area, whereas the EDF model assigns the largest
share to the China-Africa area (with personal travel making up the bulk of the
demand).

Table 9-22 provides data on passenger demand from
the EDF and FESG models by region in 1990 and 2050 and regional distribution
of world GNP and population over the same time periods. The basis of both models
in this comparison is the IS92a GNP and population scenario. In 1990, the demand
distributions of both models are roughly the same and reflect to a great extent
the regional distribution of GNP. In 2050, the regional demand distribution
from the FESG model reflects the shift in GNP distribution, demonstrating the
economics-driven basis of the FESG model. The 2050 FESG values also show that
the market share tool has probably underestimated the share of demand in region
4; percentage of GNP has increased from 1990 to 2050, but percentage of demand
has decreased.

In contrast, the 2050 demand distribution from the EDF model differs greatly
from the distribution of GNP in 2050 and reflects the population-driven basis
of much of the EDF model.

The differences between the FESG and EDF models are further illustrated in
Figures 9-28 and 9-29, which
show the cumulative distribution of traffic growth over time for the IS92a scenario.
Figure 9-28 shows the growth and regional proportions
of traffic demand as projected by the FESG model. The shares of demand reflect
the GDP of each region. Figure 9-29 shows the cumulative
distribution of demand for the five regions as projected by the EDF model. The
EDF model, unlike the FESG model, projects

business and personal passenger demand separately (business demand is a function
of GNP; personal demand is a function of population); both sectors of demand
are shown in the figure. Notable is the lack of projected growth in personal
demand in region 1 (OECD less Japan). Driven by projected slow growth and eventual
decline in OECD population, demand growth in this sector is projected to be
less than 1% per year after 2005 and negative after 2035. Notable also is the
relative lack of growth projected for region 2 (Asian newly industrialized countries
+ Japan). The effect of the population-driven personal demand sector is shown
by the rapid growth in regions 3 (China + rest of Asia) and 4 (Africa, Latin
America, Middle East). Personal demand in these two regions is projected by
the EDF model to grow at rates exceeding 12% per year for 25 years (region 3)
and 10% per year for 20 years (region 4) to create 75% of total passenger demand
in 2050 (up from 19% in 1990). This value contrasts with the 21% of total passenger
demand projected for these two regions in the FESG model, based on the two regions'
33% share of GNP.

9.6.4. NOx Technology Projections

A list of NOx emissions index projections is given in Table
9-23 for the three long-term models (IS92a scenarios).

The fleet EI(NOx) in 1992 was calculated as 12.0 (NASA), 13.8 (ANCAT/EC2),
and 13.9 (DLR).

Expectations for the development of NOx technology are quite different among
the models. The two FESG model NOx technology estimates were based on ICCAIA
technology projections for new aircraft (Sutkus, 1997) and estimates of how
quickly such new technology would enter the fleet (Greene and Meisenheimer,
997). The assumptions in the DTI model were that regulatory pressures would
require reductions in NOx emissions, and the fleet emissions index would be
forced down as the engine industry responded with specific technology developments
through 2035. These developments assumed the introduction of emission control
technology that would produce engine emissions indices appropriate to those
anticipated for staged combustor and ultra-low NOx combustor technology-the
latter of the type being developed for HSCT applications [EI(NOx) =5]. Ultra-low
NOx technology concepts now being developed may not be suitable for future high
pressure ratio subsonic engine designs, so achieving fleet NOx emission levels
assumed in the DTI and EDF models may be very difficult (see Section
7.5).

The EDF model used a logistic extrapolation of NOx trends from NASA work (Stolarski
and Wesoky, 1993), but no changes in technology were explicitly specified.

Table 9-24: Projected traffic and size of global fleet.

Traffic (RPK x 109) and Global Flee

Scenario

Year
1990 (*1995)

Year
2050

Fleeta)

Eab

2,171

23,256

35,000

Eeh

2,171

46,362

69,000

Fa1,2

2,536*

13,934

21,000

Fc1,2

2,536*

7,800

15,000

DTI

2,553

18,106

30,000

aPassenger fleet rounded to nearest 1000.

Table 9-25: Effect of freighter fleet on 2050 total fleet size

Sector

Current
Fleet

2050 FleetLowest Growth

Forecasta
Highest Growth

Passenger

10,000

5,000 (Fc1,2)

69,000 (Eeh)

Freighter

1,347

8,000
(2.5% growth)

19,000
(5.1% growth)

Total Fleet

11,347

23,000

88,000

aRounded to nearest 1000

Table 9-26: Number of new airports required to accommodate year
2050 fleet.